The present invention relates to an improved pressure transmitter. Pressure transmitters have been used to sense a signal pressure and provide an indication of such signal pressure as an output in a pressure range which is substantially reduced with respect to the signal pressure. Such output is commonly conducted to a pressure gage which is calibrated to read the larger signal pressure. Such devices eliminate the need for conducting the high pressure signal to the gage which reduces costs and eliminates the danger of high pressure equipment. FIG. 1 of the drawings is an example of such prior art pressure transmitter.
Another example of a prior pressure transmitter is disclosed in U.S. Pat. No. 4,193,307 to Baker et al. This device is used as a part of a system to provide an indication of subsea well head pressure to the surface.
One disadvantage of the prior pressure transmitters is that the tolerances on the effective pressure areas need to be small to ensure the accuracy of the desired output range.
The prior art contains many structures such as valves and gages which provide an accessible adjustment to adjust the gage reading (U.S. Pat. Nos. 32,514, 2,297,679 and 4,166,396), to adjust a cable tension sensing device for changes in the mechanical advantages used in the cable system (U.S. Pat. No. 2,013,810) and to adjust the sensitivity of valve positioners (disclosed in Control Valves by Chester S. Beard, Instruments Publishing Company, 1960--pages 150 through 167). The gage adjustment involves the shifting of the pivot point of a beam interposed between the pressure sensing element and the pressure indicating element to provide a correction of the gage reading. The adjustment feature of the above mentioned valve positioners includes the movement of a pivot pin in a system of levers.
While such adjustment features are known in the prior valve and gage art, no adjustment has been suggested for a pressure transmitter which would be easy and simple to incorporate therein without a substantial increase in cost.